This invention relates generally to coaxial connectors, and more specifically to the implementation of multiple molded plastic coaxial connections in a stacking connector for a mini PCI card.
Space-constrained mobile computing systems (MCSs) such as notebook and laptop computers and PDAs use miniature versions of PCI cards (Mini PCI cards). Mini PCI cards are cards with wired functionality and are the equivalent for a MCS of the option cards of a personal computer. These cards may be only 40 mm by 60 mm compared to a standard PCI card which may typically be 20 cmxc3x978 cm. Multi-function mini PCI cards (cards) that implement wireless functions in a MCS require a means for connecting one or more antennas to the card. For example, currently, two wireless standards being implemented in MCSs are the Institute of Electrical and Electronic Engineers"" (IEEE) wireless LAN equipment standards IEEE Standard 802.11a (operating frequency 5.2 GHz) and IEEE Standard 802.11b (operating frequency 2.4 GHz). A card may require two antennas to support each of these standards, for a total of four antennas to support both standards.
A major consideration in implementing an antenna is to achieve a low loss connection. To provide low loss, the characteristic impedance of the connection must match that of the antenna. This means that the characteristic impedance of the connection must remain stable, ideally over a wide frequency range. A coaxial connection is one suitable connection for the transmission of high frequency signals. Coaxial connectors have an outer conductor separated, by a dielectric material, from an inner conductor. The diameter of the inner conductor, the diameter of the outer conductor, and the dielectric constant of the material separating them, determines the characteristic impedance of the connection.
FIG. 1A illustrates a typical card with four coaxial connectors in accordance with the prior art. System 100, shown in FIG. 1A, includes a motherboard 105. The motherboard is the main circuit board for the MCS and typically includes the CPU, bus, and other components. A card 115 may be connected (interfaced) to the motherboard 105 via a stacking system connector 110. A typical stacking system connector may have 100 or more pins and be 4 mm or less in height. The example card 115 contains a set of four coaxial connectors 120 along with other components 125. The set of coaxial connectors 120 may be any one of various familiar types of coaxial connector such as SMA, BNC, subminiature coax, or others. Each of the coaxial connectors 120 is connected via a coaxial cable to an antenna, not shown. FIG. 1B is a side view of system 100 and includes antenna 130B connected via coaxial connectors 120 directly to card 115.
This scheme has a number of drawbacks. The first is that the coaxial connectors, though small, still take up a considerable amount of the card space. Another drawback is that having four cables connected to the card adds to the connection complexity and increases the likelihood of a misconnection. Also, four cables floating around in the highly space-constrained MCS add significantly to the chance of shorting out other components. If the solution is build to order/configure to order, the chance of putting the wrong cable on a connector is very high.
Placing the coaxial connectors within a stacking system connector (i.e., feeding the RF signal through the stacking system connector) would address most of these concerns. The cables could be permanently attached to the motherboard. Then when a card is plugged in a connection would be made between the card and the antennas through the motherboard. However, coaxial connectors, as they are currently manufactured, present several obstacles to being implemented within a stacking connector system. First, even the smallest of coaxial connectors are relatively large compared to a stacking connector system. Second, a typical coaxial connector has some individually machined components that are expensive and tend to increase the size of the coaxial connector.
FIG. 2A illustrates several coaxial connectors in accordance with the prior art. Connector 200 has four coaxial connectors 201-204 each having individually machine parts. Due to the tolerance buildup across connector 200 the coaxial connectors cannot be fixed within housing 205. In order for the coaxial connectors to line up for proper mating some mechanical floating is necessary within housing 205. That is the coaxial connectors must be able to shift slightly for proper mating.
FIG. 2B illustrates a side view of coaxial connectors 201 and 202. The socket of each connector is not fixed within plastic 207, but is able to shift. The buildup of tolerances over several coaxial connectors tends to increase the size of connector 200.